The present disclosure relates to a weatherstrip assembly that includes dissimilar metals, and an associated method of isolating dissimilar metals in the assembly.
Commonly owned U.S. Pat. No. 5,618,593 discloses a weatherstrip molding having a an EPDM body with a first portion having a durometer hardness (approximately 90 Shore A or greater) greater than that of the remainder of the body (a durometer hardness no greater than approximately 70 Shore A). A laminated film is bonded onto the first portion of the body, with the laminated film including a layer of FLUOREX® (a weatherable polymeric product which comprises polyvinylidene fluoride as the major constituent) and a layer of polypropylene. FLUOREX® is a registered trademark of the Rexham Corporation of Matthews, N.C. Preferably, especially in belt weatherstrips and glass run weatherstrips, a metal reinforcing core is included, with the EPDM body being coextruded onto the core. In such applications, a flock or low friction layer or coating material is adhered to the second portion of the body.
The weatherstrip assembly with the laminated film material bonded onto the first portion of the body offers improved characteristics in terms of better weatherability and damage resistance for the decorative laminated film, while still retaining the sealing capabilities of the remainder of the body. In addition, the laminated film provides superior results in terms of resistance to ultraviolet rays, salt solutions, oxidation, and other environmental conditions.
Galvanic corrosion is a well-known process that results from two different metals with different electrical potentials being in electrical contact, and one of the metals corrodes. This corrosive action occurs when an electrolyte is present. The electrolyte allows the metallic ions from one metal to migrate to the other metal due to the differing electrical potentials. Although this action may be desirable in some situations (e.g., a battery), galvanic corrosion is not desirable in other instances such as structural components mounted on automotive vehicles.
In a modified version of the weatherstrip assembly described in the commonly owned U.S. Pat. No. 5,618,593, a bright strip or metal cap is provided along a portion of an external show surface of the weatherstrip assembly. Oftentimes, the metal cap is a stainless steel structure and the underlying carrier is a dissimilar metal, such as a different steel or more commonly an aluminum carrier incorporated into the weatherstrip assembly. When exposed in the environment, the potential exists that these dissimilar metals come into electrical contact, and thus result in galvanic corrosion. In an effort to address corrosion issues, the industry briefly used a mylar film sheet to isolate dissimilar metals. However, this generally did not work due to positional tolerances of the film application of the mylar film sheet during the roll forming and extrusion process associated with forming the weatherstrip. Further, during installation of the metal cap, the underlying film was caught and the physical barrier between the dissimilar metals was compromised. Vehicles in the field evidenced corrosion issues.
Accordingly a need exists for limiting the potential for galvanic corrosion in connection with an assembly such as a weatherstrip that includes dissimilar metals, and an associated method of isolating dissimilar metals in the assembly to prevent such galvanic corrosion.